CH50 (TOTAL HEMOLYTIC COMPLEMENT)

CLINICAL UTILITY:

CH50 (Total Hemolytic Complement) is a functional hemolytic assay which demonstrates the integrity of the entire classical complement system and serves as a screen for many diseases in which serum complement levels are abnormal. The assay often is used to monitor the activity of the classical pathway, or to detect hereditary deficiencies of complement components. Total complement values are lowered in diseases which are characterized by antigen-antibody reactions. Thus, complement levels fall in active SLE, reflecting the consumption of complement by immune complexes. Serial measurements of total complement can be useful in following the course of such diseases.

A marked reduction of hemolytic activity can also result from hereditary deficiencies of complement proteins, since one missing protein in the complement cascade interrupts the complement-mediated cell lysis. Complement depletion is also caused by activation of the alternative pathway in certain infectious diseases and some forms of glomerulonephritis. Since CH50 is valuable as a screening tool for the entire classical complement pathway, abnormal results may be followed with tests for specific complement components.

METHOD DESCRIPTION:

The hemolytic assay is the method used to test for CH50, or total complement function. The ability of complement, when activated by antigen-antibody complexes, to produce hemolysis of sheep red blood cells, forms the basis for the CH50 test. The amount of lysis is proportional to the level of complement in the patient’s serum. The result is the dilution of patient serum causing 50% of the cells to hemolyze, as expressed in hemolytic units.

REFERENCE RANGE:

80-160 units/ml.

SPECIMEN REQUIREMENTS:

0.5 ml serum. Send on dry ice. (Complement activity decreases unless the sample is kept frozen at -70°C.)